Complement anaphylatoxin C5a is a 74-amino acid peptide generated from the fifth component of complement (C5) during complement activation (Ember et al., Immunopharmacology 38:3, 1997; Gerard, Annu Rev Immunol. 12:775, 1994). C5a acts efficiently as an anaphylatoxin stimulating cells such as leukocytes and endothelial cells, and is also a potent chemotactic factor for neutrophils and other inflammatory cells bearing C5a receptor (C5aR)1. Therefore, C5a is considered to be one of the most potent inflammatory mediators (Sumichika et al., J. Biol. Chem 277:49403, 2002). Inflammatory cells respond to nanomolar concentrations of C5a with intracellular calcium mobilization, stimulation of chemotaxis, aggregation, degranulation, and production of superoxide arions (Michael, Immunological Reviews 180:177, 2001). Some inhibitors such as peptide or non-peptide C5a receptor antagonists and anti-C5a antibody have already been reported. However, the design of low molecular weight agents which directly inactivate C5a has been a challenging problem (Michael, Immunological Reviews 180:177, 2001). 1 Abbreviations used herein: AHB, Antisense Homology Box; C-peptide, complementary peptide; EA, ethanolamine; EDC/NHS, N-ethyl-N-(dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide; NHS, N-hydroxysuccinimide; Pep-A, Peptide-A; Pep-B; Peptide-B; PL37-MAP, PL37 in multiple antigenic peptide form; RU, resonance response; SPR, surface plasmon resonance.
PL37 is a complement C5a anaphylatoxin fragment (aa 37-53) and is an Antisense Homology Box (AHB) peptide of C5a (Baranyi et al., Nature Med. 1:894, 1995; Baranyi et al., J. Immunol. 157:4591, 1996). The sequences within the AHBs were based on the molecular recognition theory which states that peptides which are encoded on opposite strands of DNA in a given reading frame show affinity in binding each other and this binding occurs as a result of the hydropathic complementary of the peptides. In addition, such sense-antisense amino acid sequences might represent both intra- and intermolecular interaction sites. Approximately 8-15-amino acid-long regions of this type were found in proteins, which we termed Antisense Homology Boxes (AHB) (Baranyi et al., Nature Med. 1:894, 1995). PL37 is an AHB of C5a, however, it is also antisense to two regions of the C5aR (Baranyi et al., J. Immunol. 157:4591, 1996). PL37 in multiple antigenic peptide form (PL37-MAP) evoked inward calcium current pulses on human neuroblastoma TGW cells or dibutyryl cyclic AMP-treated U937 cells (Baranyi et al., J. Immunol. 157:4591, 1996; Farkas et al., Neuroscience 86:903, 1998).
Because of the important role that C5a plays in mediating inflammatory responses in mammalian subjects, there remains an important need in the art for methods and compositions that can be used to effectively modulate, i.e., inhibit, modify, or enhance, C5a-mediated inflammatory responses in these subjects for investigative, diagnostic, and/or therapeutic purposes.